I put the first side pocket in place on the other side of the airplane to check the fit...

It's really hard to see here, but at the closest corner (the bottom, aft corner) of the pocket, I had enough space to fit a couple of wood shims.

These shims are just shy of 3/8" thick, so I should be able to make a new mold that is 5/16" deeper, resulting in about 40% more space in the pocket. Also, I'll probably make it about 1/4" less wide in the forward-aft direction as it's a bit of a close fit between the F-703 and F-704 bulkheads.